<!DOCTYPE html>
<html>

<head>
    <title>Example</title>
    <style type="text/css">
    /* :default选择器 从一组类似的元素中选择默认元素
    例如：提交按钮总是表单的默认按钮 
     */
        :default {
            outline: medium solid red;
        }
    </style>
</head>

<body>
    <form action="" method="POST">
        <p>
            <label for="apples">Do you like apples:</label>
        </p>
        <button type="submit">Submit Vote</button>
        <button type="reset">Reset</button>
    </form>
</body>

</html>